This is a good question: Zorro detects if a trade was closed from its appearance in the Broker's close list. But if the closing was several days ago, it's not anymore in the list and thus not detected as closed.

We had never observed such a case, so none of the Z systems has a script function for discarding a trade. You must ignore that problem for the next days, until the upcoming Zorro update. We'll provide a solution for removing a trade from Zorro's list.